Three charges q, uniform circular motion

Two spheres have a charge of q a stationary sphere between them has a charge of -q. The 2 positive spheres move like conical pendulums at a constant velocity of 12.0m/s in uniform circular motion. What is the magnitude of charge q?

2. Relevant equations

Electric Force = kq1q2/(r^2)
(mv^2)/r = Centripetal Force
Fg = mg

3. The attempt at a solution

I did some calculations but found difficulty because I don't know that mass of the two side spheres were.1. The problem statement, all variables and given/known data